Shape Matters: Apples, Olives With Normal BMI Fare Worse Than Pears

Nancy A. Melville

July 24, 2019

Postmenopausal women with a high waist circumference — or the so-called "apple" shape — even when their body mass index (BMI) is in the normal range, show an increased risk of overall, cardiovascular, and cancer mortality similar to those who are obese with a high waist circumference.

The study underscores the role of body fat distribution in health risk, say Yangbo Sun, MD, PhD, University of Iowa, Iowa City, and colleagues.

"Our findings challenge the current paradigm that measurement of abdominal fat is not recommended for individuals with normal BMI," they add in their study published this week in JAMA Network Open.

The greater risks of "apple" versus "pear" body shape — the latter being a thinner waistline tapering out at the hips — have been widely reported; however, this new research adds to the evidence by including longer-term outcomes and data on cancer deaths.

"To our knowledge, our study is the largest study with the longest follow-up period investigating the association of normal-weight central obesity with all-cause and cardiovascular disease mortality, and the first study to report the association of normal-weight central obesity with cancer mortality," the authors emphasize.

The findings, they say, should prompt a modification in guidelines for the treatment of obesity.

"The results suggest we should encourage physicians to look not only at bodyweight but also body shape when assessing a patient's health risks," said senior author Wei Bao, MD, PhD, Department of Epidemiology, University of Iowa College of Public Health, in a statement by the university.

"People with normal weight based on BMI, regardless of their central obesity, were generally considered normal in clinical practice according to current guidelines. This could lead to a missed opportunity for risk evaluation and intervention programs in this high-risk subgroup," Bao stressed.

Scale Is Not Everything

The new results indicate that, in addition to being an "apple," even a body type that might be labeled an "olive-on-a-toothpick" may be deleterious, note the authors of an accompanying editorial.

"[The study] is a reminder that the scale is not everything," write Lilian Golzarri-Arroyo, MS, and colleagues, who are with Indiana University, Bloomington.

"We all intuitively know that BMI, which is calculated as weight in kilograms divided by height in meters squared, is a function of total mass and not just fat mass, but we may be mistaken into thinking that those with low BMI are ipso facto fit and at low risk."

Central Obesity Associated With Premature CVD and Cancer Deaths

For their prospective study, Sun and colleagues evaluated data on 156,624 postmenopausal women with a mean age of 63 years who were enrolled at 40 US centers from 1993 to 1998 as part of the Women's Health Initiative (WHI) and who were observed continuously through February 2017.

Over the two-decade follow-up, there were a total of 43,838 deaths, including 12,965 (29.6%) related to cardiovascular disease and 11,828 (27.0%) deaths from cancer.

Compared with women who were normal weight and had no central obesity, women who were normal weight and had central obesity, defined as a waist circumference above 88 cm (34.6 inches), had a hazard ratio (HR) for all-cause mortality of 1.31 (95% CI, 1.20 - 1.42), after adjusting for demographic characteristics, socioeconomic status, lifestyle factors, and hormone use.

The mortality risk was similar to those with obesity and central obesity (HR, 1.30; 95% CI, 1.27 - 1.34) using the same comparator group.

Interestingly, women who were overweight but had no central obesity showed a reduced mortality rate (HR, 0.91; 95% CI, 0.89 - 0.94), as did those with obesity but no central obesity (HR, 0.93; 95% CI, 0.89 - 0.94).

Meanwhile, the mortality risk was increased for women who had a BMI in the overweight range and had central obesity (HR, 1.16; 95% CI, 1.13 - 1.20).

Drilling down into specific causes of death, the increased risk with normal weight and central obesity versus normal weight and no central obesity was observed for CVD deaths (HR, 1.25; 95% CI, 1.05 - 1.46), as well as deaths from cancer (HR, 1.20; 95% CI, 1.01 - 1.43).

The two primary causes of death in people who had normal BMI but high waist size were cardiovascular disease and obesity-related cancers.

Guidelines Overlook Waist Circumference When Weight Is Normal

The authors note that although guidelines on obesity management from groups including the American Heart Association, American College of Cardiology, and Obesity Society recommend measuring central obesity, they suggest doing so only for those who are overweight and obese but not those who are normal weight.

"These findings underscore the need for future public health guidelines to include the prevention and control of central obesity, even in individuals with normal BMI," they stress.

The results are consistent with previous smaller studies that have looked at central obesity in normal weight individuals. These studies include the National Health and Nutrition Examination Survey (NHANES) III of 7249 women (Ann Intern Med. 2015;163:827-835), as reported by Medscape Medical News, and a UK study of more than 42,000 obese women (Ann Intern Med. 2017;166:917-918). Both studies showed increased all-cause mortality that was similar to women with obesity and central obesity.

With these new data from this larger, longer-term cohort, and with cancer deaths also included, the collective evidence suggests "normal-weight central obesity is an underrecognized, high-risk phenotype for mortality," Bao and coauthors emphasize.

Factors that could explain the higher mortality rates with central obesity include the adverse effect of visceral fat and lack of protective muscle mass in the midsection, they suggest. In addition, the presence of gluteofemoral adipose tissue is linked to an improved metabolic and cardiovascular risk profile.

"Thus, a decrease in the protective gluteofemoral adipose tissue among women with normal-weight central obesity could lead to poor overall survival," the authors suggest.

Important study limitations include the fact that only postmenopausal women were included, so the findings may not be generalizable to other populations, including men or younger women.

Editorial: Is Body Shape Malleable?

In their accompanying editorial, Golzarri-Arroyo and coauthors note another important limitation: the study only shows an association and not causation.

And the collective evidence does not necessarily answer the question of how changes to an "apple" body shape, particularly in a normal weight person, could be achieved or whether, if realized, would change outcomes.

"With all of these observations, the identification of a body shape associated with higher risk does not necessarily imply that body shape is malleable or that, if body shape were modified, it would causally affect risk," the note.

"Such conclusions require other designs and data for evaluation," they indicate.

The study nevertheless "highlights not only that factors such as cardiovascular fitness, lean muscle mass, or metabolic indicators (such as various hormones and metabolites) provide important additional information about [mortality] risk, but also that simple anatomic distribution may be predictive," they conclude.

The WHI program is funded by the National Heart, Lung, and Blood Institute, National Institutes of Health (NIH), and US Department of Health and Human Services. Coauthor Rowan T. Chlebowski, MD, has reported receiving grants from the NIH, National Cancer Institute, and American Institute of Cancer Research, and personal fees from Novartis, AstraZeneca, Genentech, Amgen, Genomic Health, and Immunomedics. Coauthor JoAnn E. Manson, MD, has reported receiving grants from the NIH. Disclosures for the editorialists are listed on the journal website.

JAMA Open Network. Published July 24, 2019. Abstract, Editorial

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